Bug fixes

• [Live Proctoring] Ensure messages sent by live proctors are being retried automatically in case of a server error. This will reduce error messages seen by live proctors when sending a chat message to a student.

• [Live Proctoring] Ensure manual assignments/unassignments of proctors in the live proctoring admin dashboard are retried in case of a server error.

• [Exam takers] Fix a rare issue where one rogue student session could cause our signaling server to crash, causing a disruption in the streaming of all other exam takers.